Strange Wideband issues

[tysparks81]

Hey LGT people,

I have a strange thing happening and I'm just looking for opinions on something happening with my car.  It has been E-tuned for over a year now, and re-tuning is kind of out of the question, since I am on a Cobb AP.

My cars AF on the AEM wideband on first start up is around 14, the Cobb AP is showing 14 as well on first startup.  Once I start driving under partial throttle & full throttle AF is spot on between the Cobb AP & AEM wideband.  But once I come to a stop sign or red light the AEM wideband jumps to 16.6-17 while the Cobb AP is still showing around 14 this only really happens after driving and coming to a stop with the car still idling, no hesitation, no bucking or bogging, no stuttering. 

I had changed the rear o2, and MAF previously when I was having hesitation and wide sweeping AF numbers earlier this year, which leads me to it believe that the Bosch LSU 4.9 Sensor is failing, but before I go spend money on the sensor it would be good to have someone else validate my logic.

[subisubisu]

I am not authoritative enough to validate, but I have a replacement Bosch LSU 4.9 inbound from Summit as I type.  Mine zooms up to 18.5 shortly after it completes its start-up routine of displaying codes and finally 14.5, and I mean in a few seconds.  My internet searches led me to believe that sensor fouling is a frequent failure with the AEM system.  I believed it enough to buy another sensor.  I can let you know when I get mine installed whether it solves my problem.

[subisubisu]

Replacement sensor arrived.  Popped it in and idled the car briefly.  It showed reasonable-looking values the whole time, rich and lean in response to throttle blips, and not the 14.5 to --- march it was doing previously.  Couldn't take it for a drive this evening due to family obligations, but I expect to take it for a drive tomorrow.  If anything changes, I will report back.

[blackobxt]

When I had an aem wideband on my Sti I remember seeing exactly what you are noticing. The aem would read richer than the ap because it would only read so rich and coming to a stop the aem would read leaner than the ap. 

[tysparks81]

On 10/24/2023 at 4:09 PM, subisubisu said:

I am not authoritative enough to validate, but I have a replacement Bosch LSU 4.9 inbound from Summit as I type.  Mine zooms up to 18.5 shortly after it completes its start-up routine of displaying codes and finally 14.5, and I mean in a few seconds.  My internet searches led me to believe that sensor fouling is a frequent failure with the AEM system.  I believed it enough to buy another sensor.  I can let you know when I get mine installed whether it solves my problem.

Is the Bosch sensor less prone to the failures of the AEM sensor?

[Haze]

FWIW, all these 4.9 wideband sensors are the same other than pigtail length and occasionally the wiring connector. I got a stock sensor for a 3.5 Ecoboost F-150 from Rockauto for the Innovate WB in my XT. I think it cost me about half of what getting one through Innovate would have. Ran it through the free air calibration sequence and it works fine.

[subisubisu]

9 hours ago, tysparks81 said:

Is the Bosch sensor less prone to the failures of the AEM sensor?

I do not know.  But I did go for a drive, and it does seem to be reporting credible values now, so I presume that the original sensor was fouled and a new one was the solution.  Do I have confidence that I am not fouling this new one at the same rate?  No, I do not.